Electrical oscillation generator



NOV. 18, 1952 N M RUST ETAL 2,618,748

` ELECTRICAL OSCLLATION GENERATOR iied sept. 7, 194e 2 SHEETS- SHEET 1 Igf.

wwf/mea New. 1s, 1952 N, M, RUST ETAL 2,618,748

ELECTRICAL OSCILLTION GENERATOR Filed Sept. 7, 1946 l 2 SHEETS- SHEET 2 WVM/mrs waa/M057 cw/ 650/265 .Hmm/67W Patented Nov. 18, 1952 UNITED- STATES PTENT FF'ICILv ELECTRICAL OSCILLATION GENERATOR Nol Meyer RushrDanbury Common; Chelmsford,

George Earnshaw Partingtom Langdale, Westmorland, and Donald Leopold- Plaistowe' andy David John Fewings, ChelmsfordrEn-gland, assignors to Radio Corporationy of America,- a corporation of Delaware Application September 7, 1946,. SerialrNo. 695,532' In Great Britain February 4', 1941 Sectionl', Public Law 690, August' 8, 1946 Patent expires February 4, 1961 18 Claims. (Cl.- Z50- 36) The present invention relates to oscillation generator circuit arrangements; and particularly to circuit arrangements for generating pulses of high, or yultra-high frequency oscillations. Broadly stated, two oscillator' circuits, one a radio frequency circuit' and the other a pulse or quench frequency circuit, are operated by a single valve.

Accordingjto the invention, in oscillation generator circuits for producing grouped pulses of radio frequency energy, the anode/cathode cir-A cuit of a thermionic valve or electronv discharge device is back-coupled to the grid/cathode cir-` cuit bymeans including a transformerhaving tight couplings between its primary and secondary windings; or, if the transformer is an. auto-transformer, between two parts of its winding.

The radio. frequency oscillator circuit may be any ofv the usual` known oscillator circuits suitable forthe radio frequency required, and for ultra high frequencies will' usually consist of "liner oscillator circuits. In the pulseoscillator circuit, the Valve is back-coupled Yto a much greater degree than is necessary to sustain oscil'- lati'ons wherebyit is caused to charge up a condenser whi'ch is associated with the grid circuit and. may be connected across the grid/'cathode space sothat the grid'be'comes biased and the valve blocked untilthe charge on the condenser shall have,dissipated,` wrfhereupon` oscillation generation recommences, The frequency at which pulses are generated is controlled, mainly by this condenserand' its associated resistance.

Back coupling for the `pulse oscillator circuit maybe eiect'ed byv a transformer in the anode or cathode circuit feeding back to the grid'. The transformer. which must have tight coupling, and low seit-capacity, can be either air' or iron cored and should' be damped. Usually aniron core gives sufiicie'nt damping. Resistors across the windings can be used forV air cored transformers. The resonant frequency of the transformer must be well' above the pulse frequency.

The resistance capacity circuit for producing theV blocking action may be in either the cathode or grid circuits. Rad-io frequency chokes` are inserted between the components comprising the pulse circuit and' the valve.Y These prevent bypassing of therradio frequency. Normally either the cathode orf anode is atearth potential as regards radio frequency so-that often only two 2 choices are requiredi -Atvv ultrahi'gh frequency it willusually be found necessary to use either chokes er tunedV lines in all connections between the valve and pulse circuit. I

The invention is applicable to a transmitter circuit, a super-regenerative receiver circuit, or a circuit which can be used either as atransmitter or receiver Cso-called trans-receiver cir-vv cuit), two such circuits formingV anA eflicien't trans-receiver system.

The invention is illustrated i-ntheaccompanying drawings.`

In one circuit arrangement in accordance with the invention. illustrated inA Fig. I, a. radio frequency tuned circuit TL, comprising a condenser and inducta-nce inparallel, or as shown parallel rods with an adjustable slider, is connected betweenY the anode and grid of a triode T, the cathode of which i'sconnected to earth through aparallel connected resistance and condenser.- The anode ofthe valve is connected to the positive terminal off asource of anode potentialV energy, the negative terminal of which earthed. This connection is effected throughthe primary winding ofi a transformer TR and aV radio frequency choke CH2. The grid of the valve is connected to earth lthrougli the `secondary iwndingofthe transformer and a second radio frequency choline CH3. The two radio frequency chokes are sit--y uated between the anode, or grid, and the primary winding, or secondary winding, as the case may be. A blocking condenser BC is included between the anode of. the valve and thatendof ther radiofrequency tuned circuit which i'svc'onnected thereto'.r

In anothercircuit arrangement in accordance with the invention (illustrated in Fig. 2l, atuned lineV circuit TL, comprising a` pair of copper rods with an adjustable slider,l is connected' between the anode and grid of4 a triode T, the interna-l capacity of whichv issuch as to permit ofult'ra high frequency working;H 'Ehe cathode of the tricdeis' connected to cai-tir through ariadio frequency chokeCI-Il.- A'lhe anode of the trode is" connected through a radio frequency choke1 CH2 toone end of anv auto-transformerAT, the other end-of which is connected 'through a condenser C and resistance-Rte earthi1 `Anode4 potential is applied to atapping point on the'V autostransformer; The junction point of the condenser and resists 3 ance is connected to the grid of the triode through a radio frequency choke CHS, Blocking condensers BC are included between the tuned line circuit and the anode and grid of the triode.

In a further circuit arrangement in accordance with the invention, which arrangement (illustrated in Fig. 6) is generally similar to the arrangement of Fig. 2, a triode T, the internal capacity of which is suiciently low for ultra short wave working, has connected to its grid and anode a tuned circuit TL comprising a pair of copper rods bridged at the remote end by a variable tuning condenser VC, instead of the adjustable slider shown in Fig. 2, which condenser is adjusted to have a value approximately equal to the anode/grid capacity of the valve and the lengths of the copper tubes of the tuned line circuit 'IL are adjusted so that the whole circuit resonates at the desired ultra high frequency. The cathode of the triode is connected to earth through a radio frequency choke (as shown) or if desired by a resistance and condenser in parallel (as shown in Fig. 1). The rest of the circuit is similar to that just described in connection with Fig. 2, except that the center point of that rod which is connected to the anode is connected to one end of the auto-transformer AT, and the junction point of the condenser C and resistance R is connected to the center point of the other rod. Blocking condensers are not required in this circuit.

Many modifications of the circuit arrangements are possible. Thus the tuned circuits TL of any of the arrangements may, as has been stated for the arrangement of Fig. 1, consist of a condenser and inductance in parallel, or it may take the form shown in Figs. 1-5, or it may take the form shown in Fig. 6.

Again, as illustrated in Fig. 5, a pair of triodes TI and T2 may have their grids connected respectively one to one end and the other to the other end of a radio frequency tuned circuit RFC, their anodes being connected together through an inductance L and their cathodes being connected together and to earth. The center point of the inductance element of the radio frequency tuned circuit is connected through a radio frequency choke CH3 and a condenser C to one end of an auto-transformer AT, the other end of which is connected through a radio frequency choke CH2 to the center point of the inductance L connecting the anodes. A resistance BR is connected at one end to the junction point of the radio frequency choke CH3 with the condenser C, and at the other end to earth. Anode potential is applied to a tapping point on the auto-transformer.

Where the oscillation generator circuit arrangement of the present invention is used as part of a pulse transmitter, modulation of the trains of pulses of radio frequency energy may be effected by modulating by means of a transformer TR the anode supply Voltage in conventional manner, as illustrated in Fig. 3. With a similar circuit for the receiver, the pulse frequencies will lock and demodulation takes place in the normal way of a super-regenerative detector. Apart from the addition of transformer TR for modulating the anode current, the arrangement of Fig. 3 is very similar to that of Fig. 2. The mid-point of the auto-transformer is connected to the negative (earthed) terminal of the high tension supply with the consequence that a blocking condenser is required between the anode of valve T and the auto-transformer instead of between the grid and the auto-transformer.

If the modulation is applied, as illustrated in Fig. 4, in seires with the blocking resistance BR, then the amplitude modulation will be very small but there will be a large frequency modulation of the pulse frequency.

With a similar circuit for reception, the pulse frequency is entrained and demodulation occurs, since the mean feed to the valve is a function of the pulse frequency.

When used as super-regenerative receivers, the output can be taken from the anode, cathode or even grid circuits, usually through a low pass filter with low input impedance at the pulse frequency.

The receiving adjustments are necessarily different from those required for a transmitter working on the same basic circuit.

The slope of the entering edge of the receiver wave and the wave form at decay need not be so steep as in the transmitter case. 'I'his is obvious for known reasons in the art of super-regeneration. The high tension voltage will ordinarily be lower for example as it is not required to swing the valve t0 limit.

Since it is found that a receiver employing a pulse oscillation generator (according to the invention) will entrain itself to the pulses of a transmitter employing a pulse oscillation generator (according to the invention), two such stations each adapted t0 operate either as a transmitter or receiver may be employed to constitute a complete radio communication system. Here the principal requirement in changing from transmission to reception is to reduce the high tension voltage at the plate by inserting a resistance in series, though for short distance cornmunication change of adjustments is unnecessary. This is convenient when receiving norma modulated C. W. for example. l

With suitable precautions to avoid dead-end effects of idle parts of the tuning circuit due to the ultra high frequency line system, the circuit can easily be made to super-regenerate from 60-150 cms. By careful choice of chokes (including those in the anode. grid, and cathode leads) and by mounting valve clips right on to the end of the line condensers (making the line condensers integral with the ends of the line), the range can be extended down to 45 cms. at the expense of the other end of the range. With given xed chokes a two to one wavelength range can be secured. Using special variable chokes, a full range of from 45-150 cms. can be secured. Using an acorn type triode, 360 volts H. T. can be used with a direct current battery feed of less than 2 milliamps. Super-regeneration adjustments remain practically constant from 50 cms. upwards, but 4become critical below 50 cms.

At ultra high frequency, where the decay time of oscillations is relatively small, the length of pulse produced is in the main controlled by the natural period of the pulse transformer and is approximately equal to this period. The frequency of repetition of the pulse is however substantially a function of the time constant of the resistance capacity blocking circuit. For instance, a pulse transformer that worked very satisfactorily had a natural frequency of 200 kc./s. and the repetition frequency was 15-50 kc.

An outstanding feature of all the circuits descr1bed was the ease with which it was possible to drive the pulse to relatively high peak powers. For instance, without straining the valve, and

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withoutV reaching limiting conditions, it was found possible todrive anacorn type tube @(usng the vgrid blocking circuit) toa peak emission Aof over 600 milliamps .corresponding to apeak power of 180 watts.-

In experiments which we have made, modulation was (in thefcasel ofr the grid blocking ar rangement) veffected by inserting. za :microphone transformer' at "the base of the vgrid 'resistance and directly modulating lfrom an ordinary `telephone microphone.` -Ample modulation, substantially 'frequency .modulation of the pulse repetition frequency, was .found to be obtained by this arrangement.

.It is to `be understood that for a receiver the oscillations do not (when the receiver is quiescent, thatis, not receiving) build -up to any appreciable strength, `that is, they are incipient. The term oscillation generator is to be understood to cover such'acase. o l

What is claimed is:

1. A radio'frequency loscilla/tion generator circuit Afor producing pulses `ofhigh frequency lor-Aof ultra high frequencyoscillations comprising an electron discharge valve-'having electrodesy ncluding lan anode, .gridrand cathode, vthe anode/cathode -circuit Iof said electron ldischarge valve being back-coupledto 'the grid/cathode circuit by means including a transformer having one windingy in *the fanod-'e'cathod'e circuit ofthe valve and a tightly coupled 4second vwinding in the Ygrid/cathodecircuit of said valve, rand a tuned radio-frequency circuit includingan inductance and a condenser in -parallelconnected acrossxthe grid/anode space =of the valve.

2. A radio frequency oscillation generator lcircuit forvproducing pulses of high lfrequency or of ultra high -frequency `oscillations comprising an electron discharge valve having Velectrodes including an anode, grid vand cathode, the'anode/cathode `circuit of said 'electron Ydischarge valve being back-'coupled to: the grid/cathode circuit by means including a transformer having one winding in the anode/cathode circuit of the valve and va tightly Vcoupled 'second winding in the grid/cathode circuit 4of lsaid valve, and a tuned radio frequency circuit, including parallel conductors terminated by a slider the Vposition, oi which vis adjustable, jconnected across the grid/anode space vof the valve.

3. In a signaling apparatus, a high frequency generator including an electron discharge device having electrodes including an' anode, grid and cathode; a Vtransmissionjline coupled to the grid vand anode for the production of high frequency oscillations; and apparatus vto interrupt the generation of said oscillations ata pulse rate including a, circuit 'of lower frequency regeneratively coupling said anode, cathode and.` control ,grid for the production of Yoscillations of said .lower frequency.

4. In a signaling apparatus, a high 'frequency generator including `an electron discharge device having electrodesincluding an anode, grid and cathode, means coupled. vto the grid and anode for the production of high frequency oscillations; and apparatus to interrupt the generation of said oscillationsV at 'a pulse rate including acircuit of lower frequency `regeneratively. coupling said anode, cathode and control .grid vfor the production of oscillations of said flower frequency.

5. A radio frequency oscillationjgenerator circuit for'producing pulses of high frequency or of ultra high frequency Voscillations comprising :a 'source of anode potential, an electron discharge valve having electrodes including an anode, grid and cathode, the anode/cathode :circuit .of said valve being back-.coupled `to the grid/cathode ,cir-.- cuit by means including an4 auto-transformer having'one part :of Vits winding in the .anode/ cathode circuit of said valve iandla :second part of :its winding connected to said grid Vby means including-a capacityand to the cathode by means including. said capacity and a resistance, and a tuned radio frequency circuit, ,including parallel conductors terminated by fa @condenser the vfea-- pacity of which is approximately equalgto the anode/grid capacity of the valve, lconnected across 'the grid/anode .spaceof 'the valve.- -6. A radio frequency oscillation 'generator -cirf cuit `vforproducing `pulses fof high .'frequencyyzor of ultra-lhigh--frequency oscillations vcomprising an -elect-rondischarge valve having .electrodes includ-ing 4an anode, .grid :and cathode, :the anode/cathode circuit of :said valve -being .backq coupledto the grid/cathode :circuit by .means including a--transformer having one windingin the anode/cathode lcircuit .of the valve and Va tightly coupled -second winding inthe grid/cathode circuit of said valve, Asaid one. winding. be-y ing connected in 'series withV :a radio 'frequency choke between the positive terminal of a soince of anode potential-and the Ianode .of fthe valve1 said choke being next toy the anode, aresistor and condenser connected in parallel with Aeach other between the cathode` of the valve and the negative terminal.'of-said-'source of anode po tential, and said second winding being connected in series with a second radio frequency choke between ythe grid-of :the valve .and vsaid network,

said second chokebeing next to .the grid.l

vrI. A radioferequency oscillation :generator circuit for producing-pulses of high frequencyor of vultra 'high frequency `oscillations comprising an electron discharge valve 'having electrodes including an anode, grid vandv cathode, theV an ode/cathode vcircuit jof said valve being backcoupled to theA grid/cathode-circuit by `means .including an auto-transformer having one part of its Winding in the anode/cathode circuit of the valve, and a second part of its winding in fthe grid/cathode circuit of said valversaid one part being connected in series witha parallelconnected resistor andcondenser network lbetween the negative-terminator a :source of anode potential andthe cathode of the valve, said network Vbeing next `to vtheecathode, and said second partbeing connected in series with said network and a choke, between thegrid and .cathode of the valve, `said choke vbeing next tol the grid. V8. A radio frequencyosc'illation generator :circuit for producing pulses of Ahigh frequency or of ultra high frequency oscillations comprising an electron discharge valve having electrodes iincluding an anode, .cathode and grid, the anode/cathode circuit of said valve being backcoupled to the `grid/cathode circuit by means including lan auto-transformer having 'one part of its winding in the anode/cathode circuit ofv the valve and a second part of its winding conlnected to the grid byjmeans including a capacity and the cathode Ymeans including 'said capacity and a resistor,- saidonepart being-connected in series with va radio frequency Vchoke 'between the positive terminal ofa source of anode potential and the anode of the valve, said choke being next to the anode, a'second choke connected between the cathode vof the valve and the negative terminal of said source of anode potential, `said second part being connected in series with a'series connected condenser and resistor between the said positive terminal and the negative terminal of said source of anode potential, said resistor being next to said negative terminal, and a second choke being connected between the junction point of said condenser with said resistor and the grid of the valve.

9. A radio frequency oscillation generator of high frequency or of ultra high frequency oscillations comprising an electron discharge valve having electrodes including an anode, grid and cathode, the anode/cathode circuit of said valve being back-coupled to the grid/cathode by means including an auto-transformer having its midpoint; connected to the cathode of said valve by means including a parallel connected resistance capacity network, one of its ends connected to the grid and the other of its ends connected to the anode, one part of its winding connected across elements including the anode/cathode space of said valve and a second part of its winding in the grid/cathode circuit of the valve, said one part being connected in series with a radio frequency choke, condenser, and parallel connected resistance and condenser network, between the anode and cathode of the valve, the choke and first mentioned condenser being interposed between said one part and the anode with said choke next to the anode and the network being interposed between said one part and the cathode, said second part being connected in series with a second choke and said network between the grid of said valve and the cathode of said valve, said second choke being next to the grid and the network being connected between said second part and the cathode, and the series connected first choke, anode/cathode space of the valve, and network, being connected between the positive and negative terminals of a source of anode potential.

10. A generator as claimed in claim 9, wherein the cathode of the valve is connected through a third choke to the negative terminal of the said source of anode potential.

11. A generator as claimed in claim 9, wherein the cathode is connected to the said network through a third choke.

12. In a signaling apparatus, a high frequency generator including an electron discharge device having electrodes including an anode, grid and cathode, a resonant circuit element coupled to the grid and anode for the production of high frequency oscillations, and apparatus to inter-r rupt the generation of said oscillations at a pulse `rate including a circuit of lower frequency regeneratively coupling said anode, cathode and control grid for the production of oscillations of said lower frequency.

13. An oscillation generator circuit for producing pulses of high frequency current, including a thermionic valve having at least a cathode, a grid and an anode, a tuned line circuit comprising a pair of elongated conductors connected at one end to the anode and grid respectively of said valve and having a condenser connected across the ends remote from said valve, an autotransformer having one end of the winding thereof coupled to a point intermediate the ends of the elongated conductor connected to the anode of said valve, and a further condenser coupling the other end of said winding to the point on the other elongated conductor corresponding to 'the point on the rst said conductor.

14. An oscillation generator circuit arrangement for producing pulses of high frequency oscillations, including a pair of thermionic valves each having a cathode, a grid and ananode, an inductance intercoupling the anodes, a radio frequency tuned network comprising a parallel connected inductance and condenser intercoupling the grids, an auto-transformer having a Winding, a radio frequency choke intercoupling one end of said winding and the midpoint of the inductance intercoupling the anodes, a further condenser having one terminal connected to the other end of said winding, a resistor connecting the other terminal of said further condenser to the cathodes, and a further radio frequency choke interconnecting the other terminal of said further capacitor and the inductance of said tuned network.

15. An oscillation generator circuit for producing pulses of radio frequency current, including a thermionic valve having a cathode, a grid and an anode, a tuned radio frequency circuit comprising a pair of elongated parallel conductors and means interconnecting the conductors at points tuning the circuit to the desired radio frequency, means coupling the anode and the grid individually to the conductors at the end thereof remote from said interconnecting means, an auto-transformer having a winding coupled at one end thereof to said anode, a condenser coupling the other end of said winding to said grid, and a resistor having one terminal connected between said condenser and said grid and the other terminal coupled t0 said cathode.

16. In a signalling apparatus, a circuit arrangement for modulating and demodulating a train of radio frequency pulses, including a thermionic valve having an anode, a cathode and a grid, a resonant circuit coupled to the grid and anode for the production of high frequency oscillations, apparatus to interrupt the production of said oscillations at a pulse rate of lower frequency regeneratively coupling said anode, cathode and grid for the production of oscillations of said lower frequency, a resistance element, and a transformer having one winding in which the modulating wave appears and another winding interposed in the cathode/anode circuit of said valve in series with said resistance element.

17. A circuit arrangement for translating a train of radio frequency pulses, including an electron discharge device having a cathode, a grid and an anode, a resonant circuit coupled to the grid and the anode for the production of high frequency oscillations, means to interrupt the production of said oscillations at a pulse rate of lower frequency comprising an auto-transformer having a tapped winding, one end of said winding being coupled to said grid, a condenser coupling the other end of said winding to said anode, a parallel resistance and condenser network coupling the tapping of said winding to said cathode, and means to vary the amplitude of the pulses produced comprising a transformer having a primary winding to which the modulatingwave is applied and a secondary winding, one end of said secondarywinding being resistively coupled to said anode and the other end being resistively coupled to the tapping of said autotransformer winding.

18. A circuit arrangement for translating a train of radio frequency pulses, including an electron discharge device having a cathode, a grid and an anode, a resonant circuit coupled to the grid and the anode for the production of high frequency oscillations, means to interrupt the applied and a secondary winding, one end of 10 Said secondary Winding being coupled to said anode and the other end being resistively coupled to the other end of said auto-transformer winding.

NOL MEYER RUST. GEORGE EARNSHAW PAR'INGTON. DONALD LEOPOLD PLAISTOWE. DAVID JOHN FEWINGS.

10 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,966,616 David July 17, 1934 2,083,246 Smiley June 8, 1937 2,212,202 Faudell Aug. 20, 1940 2,409,577 Matson Oct. 15, 1946 2,412,710 Bradley Deo. 17, 1946 

